Improvement in air-compressors



W. P. TATHAM, Air-Compressor.

No. 222,802. Patented Dec. 23,1879.

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WILLIAM P. TATHAM, OF PHILADELPHIA, PENNSYLVANIA.

IMPROVEMENT IN AlR-COMPRE SSORS.

Specification forming-part of Letters Patent No. 222,802, dated December23, 1879; application filed November 3, 1879. 4

To all whom it may concern Be it known that I, WILLIAM P. TATHAM, of thecity and county of Philadelphia, in the State of Pennsylvania, haveinvented a certain new and useful Improvement in Air Oompressors, ofwhich improvement the following is a specification.

The object of my invention is to provide, in an air compressingapparatus operated by the pressure of steam or other expansive fluid,suitable means for economically and advantageously applying andutilizing the operating medium by proportionately adapting thedecreasing force thereof when acting expansively to the increasingresistance of the air under and during compression.

To this end myimprovement consists in the combination ofa steam-cylinderand its reciproeating piston, a double-armed rock-shaft or bellcrankvibrated by said piston, and an air-cylinder havinga piston which isreciprocated by the vibrating rock-shaft, the steam and air pistonsbeingy respectively, connected to arms on the rock-shaft set at an angleof about ninety degrees apart, all as hereinafter more fully set forth.

In the accompanying drawings, Figure l is a sectional plan View of oneform of an aircompressor embodying myimprovement; Fig. 2, a side view,in elevation, of the same; and Fig. 3, a sectional plan view, showinganother form of the application of my improvement.

The distinctive feature of my improvement consists in applying theoperative power to the resistance to be overcome through theintermediation of two vibrating arms, the relation of which, in positionone to tlm other, is

such that the energy of the steam from the beginning to the end of thestroke of the operating-piston is accompanied by an increasing leverageof the arm to which it is connected, and a corresponding decrease ofleverage of the arm to which the compressing-piston is connectedthat isto say, as the first or power arm moves from near its dead-point to itspoint of greatest leverage and power the second or resistance armcorrespondingly moves from its point of greatest to its point of leastleverage and resistance. The application of this principle of operationmay be made in various different forms without departing from the spiritof my invention, two of into which the rod a is prolonged, and withinwhich a piston, c, is secured upon it. Steam and air pistons a and c aresimilarly secured upon a rod, a in the cylinders A and C, respectively,and the piston-rods a and a carry upon their outer ends cross-heads a awhich slide in guides a a parallel to the center lines of their rods.mounted in bearings on the bed-plate B, perpendicularly thereto andmidway between the longitudinal center lines of the cylinders A and A,has secured upon it a bell-crank composed of two arms, (I and d, thecenter lines of which form an angle of about ninety degrees.

The cross-head a of the cylinder-A is coupled by a connectingrod, E, to'a crank-pin on the arm at of the rock-shaft D, and the cross-head a ofthe cylinder A is similarly coupled by a connecting-rod, E, to acrank-pin on the arm d. The length of the connecting-rods E and E issuch that when the piston aof the cylinderA is at the extremity of itsstroke farthest from the rock-shaft, the crank-pin of the arm d, towhich said piston is connected, will stand at a point in its are ofvibration ten degrees, or thereabout, from the longitudinal center linebetween the cylinders A and A, on the side of said line adjacent to thecylinder A, and the full stroke of the piston will vibrate the arm (1through an arc of about twenty degrees less than the angle between thearms. The corresponding position of the piston a of the cylinder A willbe atthe opposite extremity of its stroke, and, at the completion of thetraverse of its arm (1 through an are, as above described, the crank-pinof said arm will oc- A rock-shaft, D, which is cupy a position tendegrees from the center line between the cylinders on the side adjacentto the cylinder A The length of stroke may be exactly regulated bysuitable stops; or, if preferred, the rock-shaft may carry an additionalarm, which is to be coupled by a connecting-rod to a crank and smallfly'wheel.

In the operation of my improvements the admission of steam behind thepiston a of the c ylinderA effects the outward movement of said pistonand the accompanying withdrawing stroke of the attached piston c of theaircylinder 0. The vibrating arm d, to which the piston-rod a isconnected, continually increases its leverage during the stroke, and theforce applied to the piston a during its outward stroke, acting throughthe arms 01 and d and connecting-rod E upon the piston-rod a, effectsthe inward movement of the steam-piston a and the accompanying forcingor compressing stroke of the piston c of the air-cylinder O, theresistance-leverage of the connected arm d, by which said piston c isforced in ward, continually decreasing from the beginnin g to the end ofthe stroke. Conversely the outward movement of the piston a effects in asimilar manner the inward movement of the piston a and the forcingstroke of the air-piston c.

Fig. 3 illustrates the application of my improvement to a doubleactin gsteam-cylinder, A, operating two single-acting air-cylinders, O 0, tworock-shafts, D, each having double arms 01 and d, as above set forth,being provided, and the operation being similar to that of the sin gleactin g cylinders before described, the forcing stroke of each of theair-pistons c and 0 being effected, under the same relation of movingparts, by the movement of the steam-piston a in the opposite direction.

The construction shown in Figs. 1 and 2 may be modified by prolongingeach of the steamcylinders, providing it with an air-piston andair-valves toward its delivery end, and dispensing with the two separateair-cylinders, two cylinders, each of which performs the function of anair and a steam cylinder, being employed in lieu of four, as in Figs. 1and 2. In such case a hollow rod is employed for each steampiston, andthe air-piston rod of each cylinder passes through the steam-piston andits hollow rod, and is coupled by a connecting-rod to an arm on therock-shaft, set at an angle of about ninety degrees with that of thesteampiston, four rock-arms, one for each steam and each air piston,being employed.

The steam and the air piston of each cylinder move in the samedirection, but at unequal rates of speed, and the inward stroke made bythe steam-piston of one cylinder effects the compressing stroke of itsown air-piston and the withdrawing stroke of the steam and air pistonsof the opposite cylinder under conditions of power and resistanceleverage similar to those which obtain in each of the two arrangementsof parts hereinbefore described.

It will be obvious that the changes of location and number of the partsin the several applications of my improvement herein described and shownare matters of constructive detail simply, and involve no Variation ineither case from the fundamental principle of my invention hereinbeforeset forth 5 and while a duplication of parts is required to constitute adouble-acting compressor, the operation of compression is performed ateach stroke by the combined action of one steam and one air piston andthe arms to which said pistons are respectively connected.

I do not limit myself to the particular relative location andarrangement herein shown and described, as the same may be greatlyvaried within my invention.

I claim as my invention and desire to secure by Letters Patent-- Thecombination, in an air-compressor, of a steam and an air piston, eachreciprocating within a cylinder, and a double-armed rockshaft orbell-crank having its arms connected, respectively, with the rods of thesteam and of the air piston, these members being combined for jointoperation to effect the compression of the airunder a decreasingleverage of the rockshaft arm of the air-piston and acorrespondingly-increasing leverage of the arm of the steam-piston,substantially as set forth.

W. l. TATHAM.

